High-voltage interface address circuit and method for gas discharge panel

ABSTRACT

There is disclosed an interface circuit for converting lowvoltage logic signal voltage pulses to high-voltage discharge manipulating voltage pulses for a gas discharge display/memory device. The interface circuit is connected such that the output thereof is referenced to the sustaining voltage for the panel. An optical couple is used to isolate the low-voltage logic source from the high-voltage operating circuit. Consult the specification for further details.

United States Patent Inventor Larry J. Schmersal 6220 Foxcroft, Toledo,Ohio 43615 851,131

July 18, 1969 Dec. 14, 1971 Appl. No. Filed Patented HIGH-VOLTAGEINTERFACE ADDRESS CIRCUIT AND METHOD FOR GAS DISCHARGE PANEL 8 Claims, 1Drawing Fig.

U.S. C1 315/169 R,

Int. Cl 11051) 41/23 Field 01 Search 315/149, 152-156, 159, 169;250/208, 209

References Cited UNITED STATES PATENTS 7/1938 Andersen 315/153 8/1939Tarbox et a1 315/153 X 2,415,177 2/1947 Hurley 315/153 X 3,037,1445/1962 LaMantia... 315/159 X 3,459,943 8/1969 Harnden 315/156 X PrimaryExaminer-John Kominski Assistant Examiner-E. R. La Roche Attorneys-E..1. Holler and Donald K. Wedding ABSTRACT: There is disclosed aninterface circuit for converting low-voltage logic signal voltage pulsesto high-voltage discharge manipulating voltage pulses for a gasdischarge display/memory device. The interface circuit is connected suchthat the output thereof is referenced to the sustaining voltage for thepanel. An optical couple is used to isolate the low-voltage logic sourcefrom the high-voltage operating circuit. Consult the specification forfurther details.

Patented Dec. 14,, 1971 ii 5 E E E 5 3 N6; 9 E s: 5 m N.

INVENTOR LARRY J, SCHMERSAL K, ad-Livy ATTORNEYS HIGH-VOLTAGE INTERFACEADDRESS CIRCUIT AND METHOD FOR GAS DISCHARGE PANEL Cross reference torelated applications. The invention is related to the subject matter ofBaker et al. application Ser. No. 686,384, filed Nov. 24, 1967, Nolanapplication Ser. No. 764,577, filed Oct. 2, 1968, Johnson et al.application Ser. No. 699,l70,filedJan. 19, 1968.

BACKGROUND OF THE INVENTION Gas discharge panels and devices of thepulsing-discharge type e.g., discharges terminated by stored charges)require relatively high operating voltages, the magnitude of whichdepends upon, among other things, the discharge gap, gas mixture andpressure, thickness of the dielectric. For example the gas dischargepanel disclosed in the above-referred Nolan application requiressustaining voltages between about 300 and 400 volts supplied toconductor matrices defining discharge sites. High-voltage pulses areadded to such sustaining voltages at selected times to manipulatedischarges at selected discharge sites. Command or information signalsfrom a computer or other source of information to be displayed and/orstored are normally at a 4-volt level and such low voltages are ofinsufficient magnitude to manipulate the discharge condition of selecteddischarge sites. In the past, low-voltage command or address voltagesfrom addressing logic circuits have been translated to voltage levelsufficient to manipulate discharges and selected discharge sites bytransformers driven by two transistors. Also, high-voltage transistorswitches actuated by the low-voltage command voltages are used toconnect a high-voltage direct current supply to conductors in thedischarge site selection matrix. In such cases, the low-voltagecircuitry may require additional components to assure isolation of thehigh-voltage supply from the low-level logic circuits.

SUMMARY OF THE INVENTION In accordance with the present invention,isolation of the low-level command voltage source is achieved by a useof an optical couple. The low-level command signal (4 volts) isconverted to a pulse of radiant energy such as light, which may bedirectly coupled, or, preferably, transmitted by a fiber optic element,to a light-sensitive transistor amplifier so that the low-leveloperating voltage, permitting different referenced grounds. Thus, thelow-voltage system can be earth ground referenced whereas thelight-sensitive amplifier can be referred to the high-level periodicvoltage necessary to sustain discharge within the discharge device at aselected site, once initiated.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other features, aspectsand details of the invention will become more apparent from thefollowing specification when considered with the accompanying drawingillustrating a preferred embodiment of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT With reference to the drawing, agas discharge panel of the type disclosed in Nolan application Ser. No.764,577 is constituted by a pair of relatively rigid support or platemembers 11 and 12, respectively, each of which has on opposing surfacesthereof conductor arrays 13 and 14, respectively, cooperatively definingdischarge site locations and a pair of thin dielectric members and 16,respectively. plate member 11 and 12 being joined together and sealed byspacer sealant member 17. The opposing surfaces of thin dielectricmembers 15 and 16 constitute at least in part a portion of storagemember forming walls of a thin gas chamber under about 10 mils thick,and preferably the gas chamber is about 4 to 6 mils thick. Transverselyoriented conductor arrays 13 and 14 are supplied with operatingpotentials for selectively effecting discharges within the this gaschamber between selected cross points or matrix points of a pair of theconductors of each array and sustaining and terminating discharges onceinitiated. The gas is one which is under a relatively high gas pressureso as to localize the discharges within the chamber and to confinecharges produced on discharge to within the volume of gas in which theyare created. As 5a forth in the aforementioned Nolan application, thegas in the thin gas chamber has a breakdown voltage versus discharge gapdistance which is relatively horizontal over a selected broad range ofgas pressure and, preferably is a mixture of neon and argon gaseswherein the neon constitutes about 99.9 percent atoms of the gas mixtureand the argon constitutes about 0.1 percent atoms of the gas mixture.The gas is under pressure of about 0.2 to about 5 atmospheres andpreferably from about 0.2 to about 1 atmosphere.

As further disclosed in the aforementioned Baker et al. and Nolanapplications, charges produced on discharge of the gas are collectedupon the discrete surface areas of dielectric members 15 and 16 and ineffect constitute electric potentials opposing the potentials whichcreated them and hence terminate the discharge. However, on a succeedinghalf-cycle of applied potential, potential of the stored charges, beingin the same direction, aid in initiating the next discharge andconstitute an electrical memory. Because of the gas being at arelatively high pressure and separated from the operating conductors bydielectric material, relatively high periodic alternating potentials arerequired in order to sustain discharges once initiated. At the presenttime, typical sustaining voltage for a neon-argon panel lies within therange of 335 to 350 volts peak to peak at a frequency or rate of fromabout 30 to 50 kHz. with Z-microsecond high-voltage pulses superimposedor added to the sustaining voltage to manipulate the discharge conditionof selected discharges sites The normal magnitude of pulse potentialrequired to initiate a discharge (assuming. of course, that the gas hasbeen condition-ed by ultraviolet or by other means as disclosed in theaforementioned patent application) is about the same as the sustainingpotential.

Nonnally voltages from a computer or standard commercially availablelogic circuitry is in a neighborhood of 4 volts. To interface suchlow-level signals with panels requiring voltages around times larger isthe problem with which the present invention deals.

As shown in the drawing, each conductor 14-1, 14-2, 14-3 14-n ofconductor array 14 and each conductor 13-1, 13-2. 13-3, l3-n ofconductor array 13 is provided with its own drive circuit.

Each row conductor in conductor array 14 and each column conductor inconductor array 13 is provided with its own driving or interfacecircuit, which in the drawing are designated as 20-1, 20-2, 20-3 and20-n for row conductors 14-1, 14-2, 14-3, 14-11 respectively, and 21-1,21-2, 21-3 and 21-n for column conductors 13. It will be appreciatedthat panel 10 will usually have many more conductors and conductorarrays 13 and 14, presently available panels having the conductors on 30mil centers so that in a 4-inch display area in a panel there may beabout 132 row conductors and 132 column conductors.

Interface circuits 20 include a switching transistor 30 of the NPN-typehaving its collector C connected through resistor 31 to the positiveterminal of a high-voltage direct current source 32 (E and its emitter Econnected to the negative terminal of high voltage direct current source32. In addition, a periodic voltage, as for example, a sinusoidalvoltage (Vs/2) from a sustaining voltage generator 33-A is applied tothe common terminal 35 or connection between the negative terminal ofbattery 32 and the emitter electrode of transistor 30. As will bedescribed later herein, the sustaining voltage from sustaining voltagegenerator 33-A constitutes one-half the sustaining potential necessaryto be applied across the gas in the discharge gap in the panel tosustain discharges once initiated. Oppositely phased sustaining voltage(Vs/2) from sustaining generator 33-8 is applied to column conductors 13through addressing pulse circuits 21.

Connected in parallel with the high-voltage direct current source 32 isa series circuit constituted by resistor 34 and photosensitive diode 36,the anode of diode 36 being connected to the common circuit point 35 foremitter electrode of transistor 30, the negative terminal of high directcurrent source 32 and the connection from sustaining generator 33-A. Thecommon point 37 between resistor 34 and photosensitive diodes 36 isconnected by a lead 38 to the base of transistor 30.

When photosensitive diode 36 is not illuminated, the resistance thereofis in the megaohm range and all of the current lbenters the base b oftransistor 30 turning this transistor on. Thus, the output voltageappearing at the collector of transistor 30 is essentially thesustaining voltage (Vs/2) from the sustaining generator 33a, passed bytransistor 30.

Photosensitive diode 36 receives signal inputs in the form of burst ofradiant energy, such as light, from a light-bearing fiber optic element40, photosensitive diode 36 being in close optically coupled relation tothe output end 40-0 of fiber optic element 40. The input end 40-1 oflight-bearing fiber element 40 is in close optically coupled relationwith respect to lightemitting diode 41, there being a light-emittingdiode 41 and fiber optic element 40 corresponding to each circuit 20with the cathodes thereof commonly connected together and to the commonsystem ground. Any 4-volt pulseas, for example, a 4- volt logic pulsefrom logic-addressing circuit 50 causes the light-emitting diode towhich it is applied to emit light. Such light is coupled by a fiberoptic element 40 to photosensitive diode 36 to cause the resistancethereof to drop from in the megaohm range to about 10,000 ohms whichthen causes the current lb to flow to ground through photosensitivediode 36. As a result, transistor 30 is turned off and the outputvoltage rises to the potential of high-voltage direct current source 32added to the sinusoidal voltage from sustaining voltage generator 33-A.Thus, this output voltage now consists of a sine voltage plus anadditive voltage e.g., (Vs/2)+E,,,,). When the diode 41 is pulsed by4-volt logic signals, then the output voltage Vs/2 will also have pulsesadded thereto of a magnitude essentially equal to source 32.

As noted earlier, the sustaining voltage sources 33A and 33-8 produceoppositely phase sustaining voltages so that one-half the requiredsustaining voltage is applied to column conductors 13 and one-half therequired sustaining voltage is applied to row conductor 14. In order toaccommodate this arrangement, pulsing circuit 21 utilizesPNP-transistors 30, and opposite polarity high-voltage direct currentsource 32 as well as an oppositely poled photosensitive diode 36', andexcept for this reversal of polarity. the operating principles areidentical, it being understood that logic signal voltages applied tolight-sensitive diodes 41 are applied simultaneously to selected pairsof conductors, the crossing points of which define a selected dischargesite which it is desired to manipulate the discharge condition thereof.

lt will be appreciated that other than sinusoidal voltages may be usedto supply sustaining potentials. For example, alternating polaritysquare waves may be used in place of a sine wave. It will also beappreciated that signal produced at the base of transistor 30 may beused to switch a current pulse through a transformer primary to inducehigh voltages in the secondary thereof. the secondary being connected inseries with a source of sustaining voltage as shown in application Ser.No. 699,170.

A feature of the circuit is that a 4-volt pulse, referenced to ground,may be used to control a very high-voltage (300 volt) pulse that isreferenced to or floats on a sine waveform or other periodic waveform.The fiber optic elements effectively isolates the two signals such thata 300-volt signal does not couple back into the 4-volt system. Inaddition, there are fewer components per interface circuit and,obviously, since transistor 30 is conducting when it is not pulsed, theline impedance is reduced thereby reducing crosstalk between matrixconductors, 1n the circuit disclosed, the high-voltage pulsing circuitis isolated from the source of control signals via the optical couplingbut other forms of isolation may be used so as to permit the pulsesignals to be referenced to the sustaining voltage.

What is claimed is:

1. For use with gas discharge devices of the type in which a thin gasdischarge medium under pressure and bounded by dielectric charge storagemembers has selected discharge sites in the gas manipulated on and ofiby relatively high-voltage pulses selectively added to a periodicsustaining voltage from a sustaining voltage source constituted by apair of sources having a common reference point therebetween, through atransverse pair of matrix conductor arrays, respectively, saidtransverse pair of matrix conductor arrays defining the discharge sitesand wherein voltages from a relatively low-voltage command voltage pulsesource determines application of said selectively applied relativelyhigh-voltage pulses, the improvement comprising,

means for converting said low-voltage pulse to a pulse of radiantenergy, and

a high-voltage direct current source,

electronic switch means responsive to said pulse of radiant energy forconnecting said high-voltage source to matrix conductors defining aselected discharge site and in series relation with respect to one ofsaid sustaining voltage sources, respectively.

2. The invention defined in claim 1 wherein said radiant energy is lightand including an optical couple between said means for converting andsaid switch means for transmitting and applying the light to said switchmeans.

3. The invention defined in claim 2 wherein said means for convertingincludes a light-emitting diode and said optical couple includes alight-bearing fiber optic element.

4. The invention defined in claim 1 wherein said switch means includes:

radiant energy responsive impedance element positioned to receive saidpulse of radiant energy,

said high-voltage source being a direct current voltage having amagnitude of potential corresponding substantially to the relativelyhigh-voltage pulses to be added to said sustaining voltage,

a transistor,

resistor means connecting the emitter-collector circuit of saidtransistor across said high-voltage source,

means connecting the base electrode of said transistor to said radiantenergy responsive impedance element, whereby on the absence of radiantenergy on said radiant energy responsive impedance element saidtransistor is rendered conductive and the presence of radiant energy onsaid radiant energy responsive element renders said transistornonconductive to cause the potential of said high-voltage source to beadded to said periodic voltage.

5. A circuit for supplying operating potentials to a gas dischargedevice of the type in which a thin gas discharge medium under pressure,and bounded by dielectric charge storage members, has the dischargecondition of selected discharge sites therein manipulated by selectivelyapplied high-voltage pulses added to a relatively high periodicsustaining voltage through a pair of transverse conductor arraysdefining the discharge sites and wherein voltages from relativelylow-voltage signal pulse source determines application of saidselectively applied relatively high-voltage pulses, the improvementscomprising:

a plurality of circuits for converting a relatively low-voltage signalpulse to a relatively high-voltage pulse,

each said circuit for converting a relatively low-voltage signal pulseto a relatively high-voltage pulse at a remote point comprising:

a light-emitting diode,

means connecting said light-emitting diode to said low-voltage signalpulse to produce a pulse of light,

a light-bearing fiber optic element having an input end and an outputend, with said input end positioned to receive light emitted by saidemitting diode,

a photosensitive diode positioned to receive light issuing from saidoutput end of said light-bearing fiber element, the dark impedance ofsaid photosensitive diode being very high,

a relatively high direct current voltage source,

a transistor having emitter, collector, and base electrodes,

means including a first resistor for connecting the emittercollectorcircuit of said transistor across said high direct current voltagesource,

means including a series resistor for connecting said photosensitivediode across said direct current voltage source,

means connecting a point intermediate said series resistor and saidphotosensitive diode to the base electrode of said transistor,

whereby in the absence of light on said photosensitive transistor basecurrent flows through said transistor rendering said transistorconductive and in the presence of light on said photosensitive diode theimpedance thereof is low and current flows through same and saidtransistor is rendered nonconductive,

and an output terminal connected to said first resistor on which appearsthe high direct current voltage from said high direct current sourceappears when said transistor is rendered nonconductive,

and means connecting said output terminal to at least one conductor inone of said arrays,

a source of said relatively high periodic sustaining voltage,

and means commonly connecting said source of relatively high periodicsustaining voltage to a terminal of said relatively high direct currentsource, whereby when said transistor in one of said circuits inconducting said source of periodic sustaining voltage is connected tosaid output terminal and when said transistor is nonconducting saidsource of periodic sustaining voltage is connected in series with saidrelatively high direct current voltage source, appears at said outputterminal with said voltage from said high direct current source.

6. In a system for supplying operating potentials to a gas dischargepanel device of the type in which a thin gas discharge medium underpressure and bounded by dielectric charge storage members has thedischarge condition of selected discharge sites therein manipulated byselectively applied high-voltage pulses and discharges maintained onceinitiated by a pair of relatively high, periodic sustaining voltagesfrom a pair of sources by means of a pair of transverse row and columnconductor arrays defining the discharge sites and wherein voltages froma relatively low-voltage signal pulse source determine the occurrence ofsaid high-voltage pulses, the improvement comprising,

each said source of sustaining potential having a pair of outputterminals, respectively, and means connecting one of said terminals fromeachsource of sustaining potential to each other and a point of commonpotential so that said relatively high sustaining voltage sources beingconnected to conductors of said array respectively such that said panelfloats with respect to a point of common potential, at least a pair ofopposite polarity high-voltage pulse generator means for the row andcolumn conductor arrays, respectively, means connecting one saidhigh-voltage generator means in series between one of said pair ofsources of periodic sustaining voltage and the row conductors of saidpanel and the other of said high-voltage pulse generator means in seriesbetween the other of said pair of sources of periodic and sustainingvoltage, means for applying said relatively low-voltage signal pulses torespective ones of said high-voltage pulse generator means to cause saidhigh-voltage generator means to generate high-voltage pulses having as areference point the magnitude of said voltage periodic voltage from theone of said pair of sources it is connected with in series relation. I7. The invention defined in claim 6 wherein said means for applying saidrelatively low-voltage signal pulses to said highvoltage pulse generatorincludes means for isolating the lowvoltage signal source from saidhigh-voltage pulse generator.

8. The invention defined in claim 7 wherein said means for isolatingincludes an optical couple,

1. For use with gas discharge devices of the type in which a thin gasdischarge medium under pressure and bounded by dielectric charge storagemembers has selected discharge sites in the gas manipulated on and offby relatively high-voltage pulses selectively added to a periodicsustaining voltage from a sustaining voltage source constituted by apair of sources having a common reference point therebetween, through atransverse pair of matrix conductor arrays, respectively, saidtransverse pair of matrix conductor arrays defining the discharge sitesand wherein voltages from a relatively low-voltage command voltage pulsesource determines application of said selectively applied relativelyhigh-voltage pulses, the improvement comprising, means for convertingsaid low-voltage pulse to a pulse of radiant energy, and a high-voltagedirect current source, electronic switch means responsive to said pulseof radiant energy for connecting said high-voltage source to matrixconductors defining a selected discharge site and in series relationwith respect to one of said sustaining voltage sources, respectively. 2.The invention defined in claim 1 wherein said radiant energy is lightand including an optical couple between said means for converting andsaid switch means for transmitting and applying the light to said switchmeans.
 3. The invention defined in claim 2 wherein said means forconverting includes a light-emitting diode and said optical coupleincludes a light-bearing fiber optic element.
 4. The invention definedin claim 1 wherein said switch means includes: radiant energy responsiveimpedance element positioned to receive said pulse of radiant energy,said high-voltage source being a direct current voltage having amagnitude of potential corresponding substantially to the relativelyhigh-voltage pulses to be added to said sustaining voltage, atransistor, resiStor means connecting the emitter-collector circuit ofsaid transistor across said high-voltage source, means connecting thebase electrode of said transistor to said radiant energy responsiveimpedance element, whereby on the absence of radiant energy on saidradiant energy responsive impedance element said transistor is renderedconductive and the presence of radiant energy on said radiant energyresponsive element renders said transistor nonconductive to cause thepotential of said high-voltage source to be added to said periodicvoltage.
 5. A circuit for supplying operating potentials to a gasdischarge device of the type in which a thin gas discharge medium underpressure, and bounded by dielectric charge storage members, has thedischarge condition of selected discharge sites therein manipulated byselectively applied high-voltage pulses added to a relatively highperiodic sustaining voltage through a pair of transverse conductorarrays defining the discharge sites and wherein voltages from relativelylow-voltage signal pulse source determines application of saidselectively applied relatively high-voltage pulses, the improvementscomprising: a plurality of circuits for converting a relativelylow-voltage signal pulse to a relatively high-voltage pulse, each saidcircuit for converting a relatively low-voltage signal pulse to arelatively high-voltage pulse at a remote point comprising: alight-emitting diode, means connecting said light-emitting diode to saidlow-voltage signal pulse to produce a pulse of light, a light-bearingfiber optic element having an input end and an output end, with saidinput end positioned to receive light emitted by said emitting diode, aphotosensitive diode positioned to receive light issuing from saidoutput end of said light-bearing fiber element, the dark impedance ofsaid photosensitive diode being very high, a relatively high directcurrent voltage source, a transistor having emitter, collector, and baseelectrodes, means including a first resistor for connecting theemitter-collector circuit of said transistor across said high directcurrent voltage source, means including a series resistor for connectingsaid photosensitive diode across said direct current voltage source,means connecting a point intermediate said series resistor and saidphotosensitive diode to the base electrode of said transistor, wherebyin the absence of light on said photosensitive transistor base currentflows through said transistor rendering said transistor conductive andin the presence of light on said photosensitive diode the impedancethereof is low and current flows through same and said transistor isrendered nonconductive, and an output terminal connected to said firstresistor on which appears the high direct current voltage from said highdirect current source appears when said transistor is renderednonconductive, and means connecting said output terminal to at least oneconductor in one of said arrays, a source of said relatively highperiodic sustaining voltage, and means commonly connecting said sourceof relatively high periodic sustaining voltage to a terminal of saidrelatively high direct current source, whereby when said transistor inone of said circuits in conducting said source of periodic sustainingvoltage is connected to said output terminal and when said transistor isnonconducting said source of periodic sustaining voltage is connected inseries with said relatively high direct current voltage source, appearsat said output terminal with said voltage from said high direct currentsource.
 6. In a system for supplying operating potentials to a gasdischarge panel device of the type in which a thin gas discharge mediumunder pressure and bounded by dielectric charge storage members has thedischarge condition of selected discharge sites therein manipulated byselectively applied high-voltage pulses and discharges maintained onceinitiated by a Pair of relatively high, periodic sustaining voltagesfrom a pair of sources by means of a pair of transverse row and columnconductor arrays defining the discharge sites and wherein voltages froma relatively low-voltage signal pulse source determine the occurrence ofsaid high-voltage pulses, the improvement comprising, each said sourceof sustaining potential having a pair of output terminals, respectively,and means connecting one of said terminals from each source ofsustaining potential to each other and a point of common potential sothat said relatively high sustaining voltage sources being connected toconductors of said array respectively such that said panel floats withrespect to a point of common potential, at least a pair of oppositepolarity high-voltage pulse generator means for the row and columnconductor arrays, respectively, means connecting one said high-voltagegenerator means in series between one of said pair of sources ofperiodic sustaining voltage and the row conductors of said panel and theother of said high-voltage pulse generator means in series between theother of said pair of sources of periodic and sustaining voltage, meansfor applying said relatively low-voltage signal pulses to respectiveones of said high-voltage pulse generator means to cause saidhigh-voltage generator means to generate high-voltage pulses having as areference point the magnitude of said voltage periodic voltage from theone of said pair of sources it is connected with in series relation. 7.The invention defined in claim 6 wherein said means for applying saidrelatively low-voltage signal pulses to said high-voltage pulsegenerator includes means for isolating the low-voltage signal sourcefrom said high-voltage pulse generator.
 8. The invention defined inclaim 7 wherein said means for isolating includes an optical couple.